1. Field of the Invention
The present invention relates to an image processing apparatus for processing an input image signal and, more particularly, to an image processing apparatus having a function of judging a feature of an input image.
2. Related Background Art
Methods of separating an image into an edge area including a character and a halftone area including a photograph image and executing proper processing for the separated areas are proposed in the following patents or applications by the same assignee as that of the present application.
(1) U.S. Pat. No. 4,701,807
(2) U.S. patent application Ser. No. 456,615 (U.S. Pat. No. 4,953,114)
(3) U.S. patent application Ser. No. 437,310 (U.S. Pat. No. 5,018,024)
(4) U.S. Pat. No. 4,723,173
(5) U.S. patent application Ser. No. 512,494 (U.S. Pat. No. 5,267,330)
(6) U.S. Pat. No. 4,686,579
(7) U.S. Pat. No. 4,729,035
(8) U.S. Pat. No. 4,905,294
(9) U.S. Pat. No. 4,821,334
(10) U.S. patent application Ser. No. 332,384 (U.S. Pat. No. 5,301,039)
(11) U.S. patent application Ser. No. 378,488 (U.S. Pat. No. 5,029,227)
(12) U.S. patent application Ser. No. 325,020 (U.S. Pat. No. 5,572,606)
(13) U.S. patent application Ser. No. 287,627 (U.S. Pat. No. 5,177,795)
(14) U.S. patent application Ser. No. 282,896 (U.S. Pat. No. 4,926,268)
(15) U.S. patent application Ser. No. 519,500 (U.S. Pat. No. 5,113,252)
(16) U.S. patent application Ser. No. 519,448 (U.S. Pat. No. 5,239,383)
(17) U.S. patent application Ser. No. 519,447 (U.S. Pat. No. 5,119,185)
However, there is a room for improvement in the above-mentioned techniques. In particular, in some originals, a halftone area expressed by dots (or screen) is erroneously judged as an edge portion, or a very thin character is erroneously judged as a screen portion. Thus, a portion of image is subjected to undesirable processing by a so-called "judgement error", thus considerably impairing image quality.
Therefore, for example, a judgement error easily occurs in an original such as a map in which characters are mixed in a screen portion, and characters are undesirably blurred.